The Ramban then quotes the Greek philosophers who disagree with Chazal

ועל דעת חכמי הפלוספי היונים כל גוף העובר מדם האשה אין בו לאיש אלא ... שהוא נותן צורהAnd the Greek philosphers say that the all of the body of the child comes from the blood of the women the only thing that comes from the man is the tzura (whatever that means)

The Ramban clearly and unequivocally records the opinion of the Greek philosophers who argue on a scientific opinion of Chazal.

This is the same Ramban who is the foundation of much of Jewish thought today and who was a great mystic/kabbalist.